light absorption and effects of pH on conjugated double bonds
Hypothesis:
the pigment fucoxanthin will be least stable at around 3 pH
Journal Article:
see sources
Lab Procedure:
Apparatus & Chemicals Needed
spectrophotometer, hot plate, pH buffers
Safety Information:
Chemicals/Reaction
pH buffers should be made carefully and not come in contact with skin
Other Information:
Abstract STABILITY OF ALGAE PIGMENTS IN VARYING PH LEVELS Amy Loushin, Nick Scott.
The purpose of this lab is to test the stability of three common pigments found in algae, and other pigments found in several common fruits and vegetables, for their stability across varying pH levels. These pigments have been found to be powerful antioxidants, anti-inflammatories, and able to fight some forms of cancer. They could be very useful as dyes for foods and medicines that would also provide their own positive health benefits. The stability of pigments from four seaweed samples and four fruit/vegetable samples was determined by combining them with buffer solutions and measuring the wavelength of maximum absorbance with a spectrophotometer. It was found that the seaweed pigments are not stable in extreme pHs (2, 12), although they were relatively stable in pHs closer to neutral (4, 7, 10). In extreme pH levels, the color of these pigments could be altered, making them not ideal as food dyes. The fruit and vegetable pigments were less stable, and some, like apple and lettuce, even exhibited visible color changes and the pH was altered. In the future, these pigments could be tested with a larger range of pHs and the pigments could be tested for stability with other variables besides pH (temperature etc.).
Stability, pH, carotenoid, pigment, Fucoxanthin, Phycocyanin, Phycoerythrin, spectrophotometer.
Results:
pH2
pH4
pH7
pH10
pH12
Ao Nori (Phycocyanin)
0.56
0.22
0.19
0.21
0.61
Hijiki (Fucoxanthin)
2.16
1.16
1.24
1.29
2.40
Kombu (Fucoxanthin)
0.19
0.30
0.33
0.34
0.45
Ana Yaki Nori (Phycoerythrin)
0.21
0.12
0.18
0.16
0.22
Fig. 2: peak absorbency levels of pigment concentrates at a range of pH levels.
pH 4
pH 7
pH 10
Apple
0.49
0.57
1,04
Lettuce
1.62
0.77
1.60
Tomato
0.34
0.69
0.75
Orange
1.25
1.01
1.51
Fig. 2: peak absorbency levels of pigment concentrates at a range of pH values
Sources:
Duangsee, Rachen. "Phycocyanin extraction from Spirulina platensis and extract stability under various pH and temperature." Diss. Print.
Hii, Siew-Ling. "Stability Studies of Fucoxanthin From Sargassum Binderi ." Diss. Universiti Tunku Abdul Rahman, Print.
Liu, Lu-Ning. "Probing the pH sensitivity of R-phycoerythrin: Investigations of active conformational and functional variation." Diss. Shandong University, Print.
Mortensen, Alan. "Kinetics and Mechanism of the Primary Steps of Degradation of Carotenoids by Acid in Homogenous Solution." Diss. Royal Veterinary and Agricultural University, Print.
"Pigment." Wikipedia. N.p., February 27 2012. Web. 7 Mar 2012. <http://en.wikipedia.org/wiki/Pigment>.
Chemicals/Reaction
Abstract
STABILITY OF ALGAE PIGMENTS IN VARYING PH LEVELS
Amy Loushin, Nick Scott.
The purpose of this lab is to test the stability of three common pigments found in algae, and other pigments found in several common fruits and vegetables, for their stability across varying pH levels. These pigments have been found to be powerful antioxidants, anti-inflammatories, and able to fight some forms of cancer. They could be very useful as dyes for foods and medicines that would also provide their own positive health benefits. The stability of pigments from four seaweed samples and four fruit/vegetable samples was determined by combining them with buffer solutions and measuring the wavelength of maximum absorbance with a spectrophotometer. It was found that the seaweed pigments are not stable in extreme pHs (2, 12), although they were relatively stable in pHs closer to neutral (4, 7, 10). In extreme pH levels, the color of these pigments could be altered, making them not ideal as food dyes. The fruit and vegetable pigments were less stable, and some, like apple and lettuce, even exhibited visible color changes and the pH was altered. In the future, these pigments could be tested with a larger range of pHs and the pigments could be tested for stability with other variables besides pH (temperature etc.).
Stability, pH, carotenoid, pigment, Fucoxanthin, Phycocyanin, Phycoerythrin, spectrophotometer.
Results:
Sources:
Duangsee, Rachen. "Phycocyanin extraction from Spirulina platensis and extract stability under various pH and temperature." Diss. Print.
Hii, Siew-Ling. "Stability Studies of Fucoxanthin From Sargassum Binderi ." Diss. Universiti Tunku Abdul Rahman, Print.
Liu, Lu-Ning. "Probing the pH sensitivity of R-phycoerythrin: Investigations of active conformational and functional variation." Diss. Shandong University, Print.
Mortensen, Alan. "Kinetics and Mechanism of the Primary Steps of Degradation of Carotenoids by Acid in Homogenous Solution." Diss. Royal Veterinary and Agricultural University, Print.
"Pigment." Wikipedia. N.p., February 27 2012. Web. 7 Mar 2012. <http://en.wikipedia.org/wiki/Pigment>.